1. Technical Field
The exemplary and non-limiting embodiments relate generally to protecting a sound transducer and, more particularly, to protecting the sound transducer from particulates.
2. Brief Description of Prior Developments
Devices, such as mobile phones for example, use a dynamic speaker and/or receiver (microphone) to receive and reproduce audio signal such as speech, music and alerting tones to a user. Such speakers/receivers are widely used in telecommunications, but also in automobile, military, medical and consumer electronics. A dynamic speaker/receiver has an internal membrane and magnet system that are vulnerable to external particles such as dust, metal particles, sand, etc.; generally identified as dust herein. The magnet system attracts metal particles which can penetrate the speaker/receiver. Metal particles are very common in many work places; especially in developing countries. It is also common to have metal particles in a pocket of trousers where keys have rubbed against each other producing metal dust.
External particle(s) entering the membrane and/or the magnet system of the speaker/receiver will deteriorate the performance of the speaker/receiver and reduce the sound quality by lowering loudness and introducing distortion until the speaker/receiver unit will totally fail.
External particle(s) at the membrane increase the force needed to move the membrane through added mass (like sand, cotton, metals, etc.) and through magnet field attraction force (ferromagnetic and ferrimagnetic instances like iron, nickel, manganese and compounds of those). This can lower the acoustic output of the speaker/receiver and introduce distortion as the EMF-motor of the speaker/receiver does not have resources to move the added mass properly; because they are designed to work only with their own mass. Especially, ferromagnetic and ferrimagnetic instances are very harmful.
External particle(s) at the membrane can cause distortion as the membrane moves due to the membrane movement; the particles bouncing back and forth inside the speaker/earpiece and hitting the membrane and other structures next to the membrane. This extra sound from impacts can be perceived as unwanted additional sound i.e. distortion. External particle(s) at the magnet system can cause rub and buzz type of distortion as the particles are hitting and scratching the moving voice coil and magnet of the speaker/receiver. This extra sound from hitting and scratching can be perceived as unwanted additional sound i.e. distortion.